Multi-phase electric circuit breaker

ABSTRACT

A low profile molded case for a multi-phase electric circuit breaker compactly houses a static trip control unit and current transformers by displacing a portion of each phase conductor strap into nestable and operative relationship with the transformers and the static units and by modifying the trip mechanism.

United States Patent Willard Sept. 25, 1973 MULTI-PI-IASE ELECTRICCIRCUIT [56] References Cited BREAKER UNITED STATES PATENTS [75]Inventor: Henry G. Willard, Wethersfield, 3,440,491 4/1969 Tenenbaum etal. 317/22 Conn.

U Primary Examiner-James D. Trammell [73] Asblgnee' 322:"; lilectncCompany New Art0rney.lohn M. Prutzman et all [22] Filed: Dec. 26, 197257 ABSTRACT [21] Appl. No.: 318,397 A low profile molded case for amulti-phase electric circuit breaker compactly houses a static tripcontrol unit and current transformers by displacing a portion of i difijg each phase conductor strap into nestable and operative 1 2 i 12 2258 relationship with the transformers and the static units and bymodifying the trip mechanism.

9 Claims, 2 Drawing Figures PATENIED SEP25I975 MULTI-PIIASE ELECTRICCIRCUIT BREAKER BACKGROUND AND SUMMARY OF THE INVENTION The presentinvention relates generally to electric circuit breakers of the moldedcase type and is more particularly concerned with a new and improvedmultiphase circuit breaker using a static or electronic trip controlcircuit.

In recent years, electric circuit breakers of the molded case type havefrequently utilized bi-metal controlled trip-latch mechanisms both aloneand in combination with current limiting fuses for overload protectionof multi-phase systems. The fuses were conveniently mounted adjacent theload end or load terminals of the circuit breakers and could be readilyremoved and replaced when necessary. This combination of electriccircuit breakers'and fuses advantageously performed the functions of aswitch and automatic interrupting mechanism. However, such anarrangement frequently required tandem or piggy back assembliesoccupying an inordinate amount of space.

It has now been found that by utilizing a static" or electronic tripcontrol unit in place of the combined bimetal and magnetic control theequivalent functions can be provided for overload protection of thesystem. Unfortunately, the static" trip control unit is of a size thatdoes not readily permit its substitution for the current limiting fusesand bi-metal assemblies utilized heretofore and therefore, it has beenfound necessary to mount the trip control unit outside the housing forthe circuit breaker. This generally necessitates the utilization ofwires outside of the circuit breaker and subjects the connections todamage during handling, storage and maintenance operations.

In accordance with the present invention, these and other disadvantageshave been obviated by redesigning, rearranging and relocating therelative positions of the various components to provide the compact andefficient housing of all components within a molded case while keepingthe case at substantially the same size as that utilized heretofore.

Another object of the present invention is the maintenance of a lowprofile molded case design for static or electronic trip controlledcircuit breakers by utilizing low profile current transformers andnestably arranging them in operative relationship with phase conductorstraps while at the same time eliminating the bimetal controlled tripunit and simplifying the trip as sembly. Included in this object is theprovision for a new and improved electric circuit breaker provided withan electronic control package or programmer fully housed within themolded case thereby eliminating the necessity for outside transformersand wires susceptible to breakage or damage during shipment, handling ormaintenance operations.

Still another object of the present invention is to provide a new andimproved electric circuit breaker design utilizing a more streamlinedand efficient trip bar construction and a magnetic trip actuating deviceresponsive to a relatively low power trip signal.

A further object of the present invention is to provide an electriccircuit breaker of the type described exhibiting an economical in-linearrangement of the separable contacts, current transformer andelectronic programming unit while at the same time effecting economiesof manufacture and improved operating characteristics without increasedsize.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

These and related objects are accomplished in accordance with thepresent invention by providing a selfcontained multi-phase electriccircuit breaker having a low profile covered insulating housing with asubstantially planar back plate and cover. A plurality of line terminalsare carried by the casing at one end thereof and corresponding loadterminals for each phase are carried by the casing remote from the lineterminals. Relatively, separable contacts for each phase are mounted inalignment with their respective line terminals and are operative forsimultaneous and common movement between open and closed circuitpositions. A phase conductor strap is provided for connecting the loadterminal of each phase to its respective separable contacts with aportion of each phase conductor strap being displaced from the backplate of the insulating case. A current transformer for each phase ismounted within the case in nestable and operative relationship with thedisplaced portion of the phase conductor strap for generating controlsignals proportional to the current flowing through said phase conductorstraps. Additionally, the circuit breaker inlcudes a static" orelectronic trip control unit responsive to signals received from thecurrent transformers for automatically tripping all phases of thebreaker simultaneously. The trip control unit as well as the currenttransformers and trip assembly are fully enclosed and housed within themolded insulating case of conventional size.

A better understanding of the invention will be obtained from thefollowing detailed description and the accompanying drawing which setforth an illustrative embodiment indicative of the way in which theprinciples of the invention are employed.

A BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a top plan view of a circuit breaker embodying the features ofthe present invention, the cover thereof being broken away for viewingthe various components housed within the casing; and

FIG. 2 is a side elevation view partially in section with the side ofthe molded casing removed to expose the components.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing ingreater detail wherein like reference numerals indicate like parts inboth figures, a tri-phase electric circuit breaker is illustrated asembodying the present invention. The circuit breaker is comprised of agenerally rectangular insulating case 10 of durable molded construction,such as a case made of a polyester-fiberglass insulating material. Thecovered case includes a box-like base portion 112 having a generallyplanar insulating back plate M, integral side walls 16 upstanding fromthe back plate along the entire length of the circuit breaker andapertured end walls 18 and 20 provided with a plurality of terminallocating recesses or carrels, designated by the numeral 22 and 24respectively. In the embodiment illustrated, the carrels on oppositeends of the breaker are positioned in alignment for receiving theirrespective line and load terminals 26, 2%. It will be understood, of

course, that the relative location of the terminals and particularly theload terminals may vary without departing from the spirit of theinvention. The electrical path between the respective line and loadterminals will be referred to as a phase such that the embodimentillustrated is a three-phase electric circuit breaker with each phaseextending along linearly the length of the circuit breaker. The severalcomponents of the circuit breaker mechanism including currenttransformers 30 for each phase and a static trip control unit 32 aremounted within the box-like base of the insulated case and are fullyenclosed by the cover of molded insulated material which rests on thewalls 16, 18 and 20 and is suitably fastened or sealed to the base toform the low profile housing for the circuit breaker.

Each line terminal 26 mounted within a separate carrel 22 is supportedby and electrically connected to a short length of conductive strap 36which extends into the interior of the case through the apertured endwall 18. The straps 36 are supported by the back plate 14 of the caseand in turn, fixedly carry stationary contacts 38 within individual archsuppressing chambers 40 located adjacent the end wall 18. A moveablecontact 42 carried by a conductive contact arm 44 is provided for eachphase of the multi-phase circuit breaker and, in conventional fashion,is pivotally supported by a contact arm mount 46 fixedly secured to acommon cross arm 48. The separable contacts are interconnected by thecommon cross arm extending fully across the circuit breaker forsimultaneous and common pivotal movement between their closed circuitposition shown in FIG. 2 and their separated or open circuit position(not shown).

A common operating mechanism suitably connected to the separablecontacts and indicated generally by the numeral 50 is provided forsimultaneously actuating all three moveable contacts 42 either manuallyor automatically between their open and closed circuit positions. Themechanism 50 includes a trip-latch 52 operatively associated with boththe contacts and the manually operated handle 54 and adapted to bedriven by the handle 54 during its movement toward its off" position. Alatching member 56 is pivotably supported on the pin 58 journalled inbracket 60 affixed to the insulating back plate 14 of the casing. Aninsulating trip bar 62 is fixedly mounted on a supporting yoke 64 whichis pivotally mounted on the bracket 60. The bracket 60 also carries anintermediate latch 66 which releasably engages and is held by the tripbar yoke 64'. The trip bar 62 includes an obliquely extending portion 68and is biased in a clockwise direction as viewed in FIG. 2 by spring 70into engagement with the end of push rod 72 controlled by the magnetictrip actuating device 74. The latching member 56 and intermediate latch66 are also biased in a clockwise direction as viewed in FIG. 2 by atorsion spring (not shown) mounted on pin 58.

Movement of the manual handle 54 to the off position will condition thetrip mechanism for a subsequent tripping operation. This operation issimilar to that described in Stokes US. Pat. No. 3,171,922 assigned tothe assignee of this application. The trip-latch 52 is driven by thehandle 54 into latching engagement with the latching member 56 causingcounterclockwise rotation thereof against the bias of its torsion springmounted on pin 58 and movement of the intermediate latch 66 against thetrip bar yoke 64 held by spring 70 against counterclockwise movement asas viewed in FIG. 2. Thus with the latch 52 held by latching member 56and the latter prevented from moving by trip bar 62, the circuit breakeris in a cocked or loaded condition. Subsequent movement of the handle 54to the on position does not alter this condition but merely rotates themoveable contacts in a clockwise direction as viewed in FIG. 2 intotheir illustrated closed circuit position.

As mentioned, the manually operated handle 54 is located centrallyacross the transverse dimension of the circuit breaker. On one sidethereof is a sensitive magnetic trip actuating device 74 suited foroperation by a relatively low power signal pulse for moving the trip bar62 in a counterclockwise direction as viewed in FIG. 2 against the biasof its retaining spring to permit release of the intermediate latch 66,latching member 56 and trip-latch 52 and effect tripping of the circuitbreaker to provide simultaneous open circuit conditions within all threephases controlled by the circuit breaker. The sensitive magnetic tripactuating device 74 is preferably of the construction and operationdescribed and claimed in my US. Pat. No. 3,693,l22 assigned to theassignee of this application. The details of construction and operationof this mechanism are fully set forth in the aforementioned patent.

The moveable contacts are electrically connected through the contactarms 44 and flexible conductors to their respective elongated phaseconductor straps 82 extending toward the load terminal end of thecircuit breaker in substantial alignment with the separable contacts,the load terminals 28 being secured to the outer end of each phaseconductor strap 82. In the embodiment illustrated, both the conductorstraps 36 mounting the stationary contacts and line terminals and thephase conductor straps 82 extending from the flexible conductors to theload terminals are mounted in intimate contact with the generally planarback plate 14 of the electrical circuit breaker. However, it is afeature of the present invention that a portion 84 of each phaseconductor strap 82 located between the load terminal and the separablecontact is displaced substantially from the back plate for passagethrough the low profile current transformers 30 associated with eachphase of the multi-phase circuit breaker.

As best seen in FIG. 1, three current transformers 30 are arranged in aside-by-side relationship across the circuit breaker with eachtransformer also being disposed in alignment with the line and loadterminals and separable contacts of its respective phase. Each of thecurrent transformers are of low profile construction and are mountedwithin the casing in a nestable and operative relationship with thedisplaced portion 84 of its respective phase conductor strap. As shown,the current transformers are of the dual winding type with the windings86 encircling complementary C-shaped cores designated generally by thenumeral 88. The windings 86 for each transformer are front to backspaced coils connected in series to provide an additive ampere turnoutput and substantially improved output due to the additive effect ofthe windings. As mentioned, the tranformers function to generate controlsignals proportional to the current flowing through the conductor strapportion 84 extending through the cores 88. By means of suitable leads 90these signals are fed to the electronic programmer or static tripcontrol unit 32.

The base 12 of the casing in the area located between the currenttransformers 30 and the load terminal 28 is divided into threelongitudinally extending channels through which run the phase conductorstraps 82. These channels are formed by the side walls 16 of the casingand by a pair of interior dividing walls 94 integrally upstanding fromthe back plate M- and extending from the end wall 20 continuously to apoint between the current transformer 30. The dividing walls 94 are eachprovided with a central notch 96 midway along their length for receivinga single electrical socket 98 to which the transformer leads 90 areconnected.

The programmer or static trip control unit 32 is a self-contained easilyremovable modular device housing solid state circuitry suited toproviding control over various conditions that might occur within any ofthe three phases controlled by the circuit breaker. As mentioned, thissolid state device is electrically and operatively connected to themagnetic trip actuating device 74 and to the current transformers bymeans of a plug 100 readily connected to the socket 98. The static tripcontrol unit 32 extends fully across the circuit breaker and rests onthe dividing walls 94 in spaced overlying and nestable relationship withthe phase conductor straps 82 which extend along the channels from thecurrent transformers 30 to the load terminal 28. The modular unit issecured to the insulating casing by means of a pair of bolted brackets102 secured to the interior walls 94 adjacent the transformer endthereof.

The substantially flat cover plate of the casing includes a separabletransparent cover portion 104 which permits visual read-out of the topcontrol panel 106 of the electronic trip control unit 32 and is providedwith a tamper-proof leaded sealing device 108 permitting authorizedremoval of the transparent portion when it is required to change thesetting on the central panel.

As willbe readily appreciated, the circuit breaker in its closedposition permits current flow from the line terminal to currenttransformer of each phase through the closed separable contact. Thecurrent transformers generate a control signal proportional to thecurrent flowing through the phase conductor straps associated therewithand the control signals are fed to the electronic programming unit whichin turn controls the operation of the sensitive magnetic trip actuatingmechanism. Accordingly, if the control signals generated by thetransformers exceed certain preselected values as determined by theelectronic trip control unit, the magnetic trip actuating device isactivated and will drive the trip bar in a counterclockwise direction asviewed in FIG. 2 against the bias of its retaining spring and releasethe latching member for simultaneous and common opening of all threeseparable contact assemblies. This "Sta tic operation obviates the' needfor a bi-metal trip control assembly or a combined bi-metal and magneticunit while providing an equivalent function with improved accuracy andrange for the long time delay and instantaneous trip functions.Additionally, the selfcontained compact unit eliminates the necessityfor wires outside the circuit breaker casing without enlarging thedesirable low. profile configuration of the circuit breaker.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

1 claim:

11. A self-contained multi-phase electric circuit breaker comprising alow profile covered insulating casing having a substantially planar backplate; a line terminal for each phase carried by the casing at one endthereof; a load terminal for each phase carried by the casing remotefrom the line terminals; separable contacts for each phase mounted inalignment with their respective line terminals and operative forsimultaneous and common movement between open and closed circuitpositions; a phase conductor strap for each phase connecting the loadterminals to their respective separable contacts, a portion of eachphase conductor strap being inwardly displaced from said back plate, anda current transformer for each phase mounted within the casing innestable and operative relationship with the displaced portion of itsrespective phase conductor strap for generating control signalsproportional to the current flowing through said phase conductor strap.

2. The circuit breaker of claim ll including a modular electronicprogramming unit carried by and within the casing adjacent the loadterminals and current transformers and in nestable relationship with aportion of said phase conductor straps other than said displacedportion, said programming unit being operatively connected to saidcurrent transformers and said separable contacts for opening saidcontacts in response to control signals generated by said currenttransformers.

3. The circuit breaker of claim 1 wherein the current transformers arelow profile dual-winding transformers with the windings connected inseries to provide an additive ampere turn output.

4. The circuit breaker of claim 3 wherein the displaced portion of eachphase conductor strap passes through its respective transformersintermediate the dual windings and in elevated relationship to the backplate.

5. The circuit breaker of claim 1 including a trip mechanism and anelectronic trip control unit, and wherein the insulating casing is amolded housing fully enclosing the separable contacts, currenttransformers, trip mechanism and electronic control unit in compactnested relationship within the low profile casing.

6. The circuit breaker of claim 11 including a static trip control unit,and a trip mechanism operatively connected to the separable contacts forrapidly moving the contacts to their open position, said trip mechanismbeing operative on said trip mechanism to open said contacts in responseto a signal from the static trip control unit.

7. The circuit breaker of claim 6 wherein the trip control unit includessolid state trip circuits and the trip mechanism includes an insulatingtrip bar for rapidly releasing the separable contacts for movementtoward their open position and a magnetic trip actuating deviceoperative for initiating the releasing operation of the trip bar, saidtrip circuits being operative in response to signals generated by thecurrent transformers associated with each phase of the circuit breakerto effect operation of the magnetic trip device.

8. The circuit breaker of claim ll wherein the load terminals arelocated at the end of said casing opposite said one end and said phaseconductor straps extend from said load terminals toward the separablecontacts in alignment with the contacts, the breaker including aself-contained static trip control unit in superimposed nestedrelationship with said phase conductor straps, said trip control unithaving a top control panel, said covered casing including a transparentcover portion permitting visual read-out of said top control panel.

9. The circuit breaker of claim 8 wherein the transparent cover portionis provided with a tamper-proof

1. A self-contained multi-phase electric circuit breaker comprising alow profile covered insulating casing having a substantially planar backplate; a line terminal for each phase carried by the casing at one endthereof; a load terminal for each phase carried by the casing remotefrom the line terminals; separable contacts for each phase mounted inalignment with their respective line terminals and operative forsimultaneous and common movement between open and closed circuitpositions; a phase conductor strap for each phase connecting the loadterminals to their respective separable contacts, a portion of eachphase conductor strap being inwardly displaced from said back plate, anda current transformer for each phase mounted within the casing innestable and operative relationship with the displaced portion of itsrespective phase conductor strap for generating control signalsproportional to the current flowing through said phase conductor strap.2. The circuit breaker of claim 1 including a modular electronicprogramming unit carried by and within the casing adjacent the loadterminals and current transformers and in nestable relationship with aportion of said phase conductor straps other than said displacedportion, said programming unit being operatively connected to saidcurrent transformers and said separable contacts for opening saidcontacts in response to control signals generated by said currenttransformers.
 3. The circuit breaker of claim 1 wherein the currenttransformers are low profile dual-winding transformers with the windingsconnected in series to provide an additive ampere turn output.
 4. Thecircuit breaker of claim 3 wherein the displaced portion of each phaseconductor strap passes through its respective transformers intermediatethe dual windings and in elevated relationship to the back plate.
 5. Thecircuit breaker of claim 1 including a trip mechanism and an electronictrip control unit, and wherein the insulating casing is a molded housingfully enclosing the separable contacts, current trAnsformers, tripmechanism and electronic control unit in compact nested relationshipwithin the low profile casing.
 6. The circuit breaker of claim 1including a static trip control unit, and a trip mechanism operativelyconnected to the separable contacts for rapidly moving the contacts totheir open position, said trip mechanism being operative on said tripmechanism to open said contacts in response to a signal from the statictrip control unit.
 7. The circuit breaker of claim 6 wherein the tripcontrol unit includes solid state trip circuits and the trip mechanismincludes an insulating trip bar for rapidly releasing the separablecontacts for movement toward their open position and a magnetic tripactuating device operative for initiating the releasing operation of thetrip bar, said trip circuits being operative in response to signalsgenerated by the current transformers associated with each phase of thecircuit breaker to effect operation of the magnetic trip device.
 8. Thecircuit breaker of claim 1 wherein the load terminals are located at theend of said casing opposite said one end and said phase conductor strapsextend from said load terminals toward the separable contacts inalignment with the contacts, the breaker including a self-containedstatic trip control unit in superimposed nested relationship with saidphase conductor straps, said trip control unit having a top controlpanel, said covered casing including a transparent cover portionpermitting visual read-out of said top control panel.
 9. The circuitbreaker of claim 8 wherein the transparent cover portion is providedwith a tamper-proof seal.